This invention relates to the production of quaternary imidazolinium fabric conditioning agents essentially free of amines, amine salts and alkoxylated forms of the quaternary imidazolinium salts. The present invention additionally relates to a fabric conditioning composition containing an imidazolinium agent essentially free of amines and amine salts and a method for conditioning fabrics.
In the conventional home laundering process, soiled fabrics are subjected to cleaning with a detergent composition in the main wash cycle and rinsing with water in the final cycle. Optionally, during the rinsing cycle a fabric conditioning composition is added. Such compositions contain a fabric softener or fabric antistat material for imparting to the rinsed fabrics softening and antistat properties. The rinsed fabrics are oftentimes, thereafter, dried in an automatic clothes dryer.
Many different types of fabric conditioning agents have been used in rinse cycle added fabric conditioning compositions. The most favored type of agent has been the quaternary ammonium compounds. These compounds may take the form of noncyclic quaternary ammonium salts having preferably two long chain alkyl groups attached to the nitrogen atom. Additionally, imidazolinium salts have been used by themselves or in combination with other agents in the treatment of fabrics. U.S. Pat. No. 2,874,074, Feb. 17, 1959, to Johnson discloses using imidazolinium salts to condition fabrics. U.S. Pat. No. 3,681,241, Aug. 1, 1972, to Rudy, and U.S. Pat. No. 3,033,704, May 8, 1962, to Sherrill et al. disclose fabric conditioning compositions containing mixtures of imidazolinium salts and other fabric conditioning agents.
While the prior art shows the use of quaternary imidazolinium salts as fabric conditioning agents, it is silent about the problems encountered in making stable fabric conditioning compositions containing such agents and aldehydes. The manufacture of imidazolinium salts generally involves the reaction of a polyamine with an acyl containing material such as an acid or ester to form an imidazoline and then a quaternizing of the imidazoline. U.S. Pat. Nos. 2,355,837, Aug. 15, 1944, and 2,267,965, Dec. 30, 1941, to Wilson; and U.S. Pat. No. 2,520,102, Aug. 22, 1950, to Tryon, all disclose methods for making imidazolines used in making imidazolinium salts. It has been found in the present invention that in addition to the imidazoline compound formed in the described reaction, primary and secondary amines are also present. During the subsequent quaternization step, these amines cause some of the imidazoline compound to form the imidazoline amine salt rather than the quaternary imidazolinium salt. The imidazoline amine salt, when present in an aqueous medium having a near neutral or higher pH, is capable of undergoing ring opening to form free amines which will then react with aldehydic compounds in the composition much the same as free amines which have not been converted to the salt form. The result is that the odor of the composition degrades (perfumes generally contain aldehydes), the color and the pH change and aldehyde preservatives degrade. The aforementioned Johnson patent describes making quaternary imidazolinium salts, but is silent about how to overcome the problems described while still achieving an end product which is sufficiently high in imidazolinium salt to be commercially attractive. In the process aspect of the present invention the undesirable amines are "capped" using an alkoxylating agent in an amount sufficient to cap the primary and secondary amines but not cap to any appreciable degree the cyclic tertiary amine which forms the imidazolinium salt.
It is, therefore, an object of this invention to provide a process for making quaternary imidazolinium salts which are essentially free of amines, amine salts and alkoxylated forms of the imidazolinium salts.
It is another object of this invention to provide a fabric conditioning composition comprising a quaternary imidazolinium salt and being essentially free of amines and amine salts.
It is still another object of this invention to provide a method for conditioning fabrics by treating them with the desired imidazolinium salts.
These and other objects will become apparent from the description which follows.
As used herein all percentages and ratios are by weight unless otherwise specified.